1. Field of the Invention
This invention relates to drum brakes, and in particular to drum brakes having an improved retaining spring structure for retaining the brake shoes pivotably to an anchor member.
2. Background of the Invention
Drum brakes having a pair of generally arcuate brake shoes pivotably mounted at one end to an anchor structure and selectively actuatable at the other ends thereof to pivot radially outwardly relative to the anchor structure to frictionally engage a brake drum are well known in the prior art. Usually, the brake shoes comprise an arcuate table carrying the friction material and at least one radially inwardly extending rib or web. Typically, the pivotably mounted ends of the brake shoe webs are formed with generally concave surfaces which are pivotably supported by an anchor structure comprising a single anchor pin, or a pair of anchor pins, fixed to the brake spider. A resilient retaining member, or members, such as a coil tension spring is utilized to retain the brake shoes against the anchor member. Examples of such prior art drum brakes may be seen by reference to U.S. Pat. Nos. 2,710,076; 3,467,229 and 3,497,037, all assigned to the assignee of this invention and all hereby incorporated by reference.
While these prior art devices are generally satisfactory and enjoy great commercial success, a problem has occasionally existed with the retaining means, or retaining springs, thereof. In particular, the retaining springs of the prior art devices usually utilized hook type ends which under certain conditions, such as vibration of the springs at or near a resonant frequency, might come free from the brake shoes and fall into the assembly. Also, the retaining springs of the prior art devices were often spaced a considerable distance from the anchor means or bended around the support means, and thus were flexed every time the brake was applied and released, thereby increasing the possibility of a failure of the retaining springs.